A diet of convenience food is popular among modern busy-working people, such that the food market is flooded with prepared food packages containing vegetable, seafood or meat. Prepared food packages are unfrozen and heated in a microwave oven before eating, and can be eaten in a very short time.
However, prepared food packages or other hermetically sealed food packages available in markets are made mostly of plastic films with low air permeability. As a result, the temperature and pressure of the air in the sealed package will be increased quickly, leading to bursting, which may damage the package during the heating of a microwave oven if the air permeation of the plastic film is insufficient and its critical tensile strength is reached.
To solve this problem, a user usually cuts an opening or poke a hole at one end of a package bag, allowing high-pressure and high-temperature air to escape through the opening or hole during the heating of the micro oven, thereby preventing internal pressure in the package from increasing suddenly to bursting point.